The biggest impact of full legalisation might be to permit research into cannabis that is currently impossible. No country has ever completely legalised marijuana. Portugal has decriminalised it and other drugs, but not legalised them. And in the Netherlands, where pot can be readily obtained in "coffee shops", possession of small amounts of cannabis is decriminalised, and producing and selling the drug remains illegal. To understand the effect of cannabis on health, researchers need to measure individuals' exposures to the drug over time and relate that to their health problems, says Matthew Hickman of the University of Bristol, UK. Doing such long-term studies in large groups of people is very difficult when use is illegal. "We can't even get good self-reported use levels," he says.
Because marijuana is illegal, it is nearly impossible for researchers to obtain up-to-date information on its effects.
Because marijuana is illegal, it is nearly impossible for researchers to obtain up-to-date information on its effects.